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2oldman

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Posted: 01/11/21 03:18pm Link  |  Quote  |  Print  |  Notify Moderator

Lynnmor wrote:

I didn't want to get onto it, but since the air dissolved into the water tells me that draining and flushing is way overdue.
I drained and flushed mine 6 months ago and it does it.

wildtoad

Blythewood, SC

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Posted: 01/11/21 03:29pm Link  |  Quote  |  Print  |  Notify Moderator

Dusty R wrote:

I like installing a small bladder type pressure tank. It makes the whole water system work nicer.


I had issue with my WH dribbling out the relief valve and none of the common remedies were effective. I had a small bladder tank installed on the cold water side of the WH and it solved my problem. And added plus was the pump did not start immediately when I turned on a faucet.


Tom Wilds
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wa8yxm

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Posted: 01/11/21 04:19pm Link  |  Quote  |  Print  |  Notify Moderator

Drain the heater than let it refill. If it's raising the pressure that much you no longer have an air cushion.

Step 2: Put an accumulator in the line, adds additional "Air cushion" (only it's not air)

Item 3: there is a valve at the top (outisde) of the heater Usually has a lever on it to manually open. The name of that is often shortened TPR. What does TPR mean.
Temperature
PRESSURE
Relief

If it's going to leak, it should be leaking there.


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TenOC

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Posted: 01/11/21 05:28pm Link  |  Quote  |  Print  |  Notify Moderator

Lynnmor wrote:

Drain the water heater and refill it, that will re-establish the air pocket in the tank and allow for expansion. .


No need to drain the water heater.
1. Turn off the pump.
2. Run hot water until no more will run.
3. Connect to city water. The hose should not have any water in it --- only air.
4. With the pump still off run some HOT water until all the air is out of the hose and in the water heater.
5. Now you can refill your freshwater tank.

The air in the hose will enter the water heater and form the air pocket.

When I connect to city water, I ALWAYS run hot water first to get the air in the hose to enter the water heater.


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Posted: 01/11/21 07:02pm Link  |  Quote  |  Print  |  Notify Moderator

Air pockets arent nearly as effective or provide the other benefits that a bladder expansion tank does. Just add the tank and you'll also have the drawdown and more stable pressure benefits.

Old-Biscuit

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Posted: 01/11/21 09:32pm Link  |  Quote  |  Print  |  Notify Moderator

Air Pocket in top of tank helps control pressure increase.
Water swells when heated.. without air pocket the internal pressure can increase enough to cause high pressure in both hot & cold systems

Only a FEW RV MFGs install check valves on Cold Inlets

Air Pockets form naturally when filling the WH Tank...same as residential WHs

Air pocket can get absorbed into the water regardless of use ...cleaning etc
RV WH Tanks are SMALL and the air pocket can easily get lost
Turn water off
Open faucet hotside to relieve pressure
OPEN T&P ---hold open until water stops flowing out
Let it SNAP Close
Close faucet...turn water on (pump or city doesn't matter)


Water heater should be heating to 130*F (Suburban) or 140*F (Atwood)

An accumulator WILL help considerably


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Posted: 01/12/21 03:01am Link  |  Quote  |  Print  |  Notify Moderator

Old-Biscuit wrote:


An accumulator WILL help considerably


A simple accumulator tank solved multiple issues for me. I would not own another RV without one.

The RV system is closed, unlike a sticks and bricks house that usually allow backflow to the city supply to relieve pressure. I have seen the RV system at a static 60psi cold, then started the Water Heater and allowed it to come to temperature without opening any fixtures to relieve the pressure.

I have seen it rise to as much as 140psi regardless of an air gap in the WH or not, this pressure revealed weak spots in my system too. I am sure this is what you are experiencing.

A simple accumulator tank will solve this issue and also provide some additional benefits as well.

Very inexpensive, easy to install and they come in sizes from one quart to two gallons for RV's or more. The bigger the better, I went with a half gallon size due to size constrictions and it works perfect.

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Dusty R

Charlotte Michigan 48813

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Posted: 01/12/21 07:41am Link  |  Quote  |  Print  |  Notify Moderator

And it does not matter where you put it, or what position it is in. Just put a Tee in the cold water line and plumb the tank into it, figure out at what pressure the pump turns on at, and add air pressure to 2 lb. below that.

mbopp

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Posted: 01/12/21 09:27am Link  |  Quote  |  Print  |  Notify Moderator

I have a 2 gallon residental expansion tank that's been in 3 trailers now. Besides stopping the drip from the TP valve it eliminates the half-cycling on the pump and also provides 1-2 toilet flushes at night w/o the pump being on.


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dougrainer

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Posted: 01/12/21 10:11am Link  |  Quote  |  Print  |  Notify Moderator

I am always amazed about perceived repairs to a simple problem.
1. I have NEVER in 41 years as an RV Tech had a specific complaint that the OP posted
2. WITHOUT the air gap in the Water heater, the pop off valve will leak once the HOT water in the tank reaches 150 psi. Without a INLET cold water Check Valve that pressure will extend to the cold water piping.
3. An accumulator tank is not needed for this specific problem. It may diminish the problem but you need to FIX the cause of the problem
4. Establish the Air Gap in the Water Heater Tank
5. Install a check valve on the Water Heater Cold Inlet. Doug

To restore the Air Gap
Turn off water heater.
Turn off incoming water supply.
Open the closest hot water faucet in the coach.
Pull handle of pressure-temperature relief valve straight out and allow water to flow until it stops.
Allow pressure-temperature relief valve to snap shut, close the faucet then turn on the water supply.

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